Method of forming and coating wood chips



June 27, 1967 E. G. HEBERLEIN 3,328,188

METHOD OF FORMING AND COATING WOOD CHIPS Filed Jan. 18, 1965 ljI/I Ill/ll/lIl/l I III III I III/I1 III'IlI/II INVENTOR, Edward GHeber/e/n SM a. 5mm

United States Patent 3,328,188 METHOD OF FORMING AND COATING W001) CHIPS Edward G. Heberlein, New Canaan, Conn., assignor to Mobil Oil Corporation, a corporation of New York Filed Jan. 18, 1965, Ser. No. 426,244 9 Claims. (Cl. 117-4) This invention relates to a method of making wood chips for particle boards. In particular this invention relates to a method of lubrication in the process of chipping wood and an apparatus utilizing the same.

Synthetic wood particle boards have been found to be a satisfactory substitute for lumber in many applications. These boards are usually prepared by cutting wood logs into small particles, coating the particles with a resinous, thermosetting binder, and molding the treated particles into the desired shape. The great advantage in using particle board is the lower cost of production since particles can be obtained from almost an entire tree, while the use of lumber necessitates a considerable wastage of the tree. Particle board manufacturing, for example, provides an extremely economical means of producing large sheets having uniform dimensions.

The first step in board manufacturing is the cutting operation. The typical apparatus for producing wood chips consists essentially of a rotatable drum or disc supporting a number of knives positioned about its periphery. A wood log is brought into aligned contact with the rotating drum or disc, and as it rotates, the knife edges, usually in the form of short wedge-like lengths, strike the wood log producing the chips. By varying the design of the apparatus, flakes, slabs, or splinters of wood may also be obtained.

In the drum cutter, for example the drum is generally rotated at very high speeds, sometimes as high as 3,000 revolutions per minute. Under such speeds and considering the varying hardnesses of the logs, the knife edges become dull in a very short time. This dulling effect is notice able in the appearance of the wood chips. The edges of the chips indicate they are being torn rather than cut and more waste dust is formed. As a result, the particle board produced from such chips would not have uniform properties, and may contain weak spots. Moreover, the resin may be wasted along these fragmented edges. Another disadvantage of this dulling of the knife edges is the increase in power required to rotate the drum. Since the knives are not cutting effectively, the force to permit the knives to cut or tear the wood log is greater. As a result, many wood chipping plants have to stop the procedure very frequently, sometimes almost every hour, to remove the knives for regrinding. It has been estimated in plants in which production rates are very high that the useful life of one knife may be from 60 to 80 hours, and the current cost required to replace badly-worn knives or to resharpen knives, including the time for shut-down of the operation, imposes a considerable economic burden on the over-all process.

A means for extending the time-period between this changeover of knives and also the useful life of the knives by preventing the rapid dulling elfect usually sulfered in the chipping operation would be an important saving in time and expense of producing wood chips. It is, therefore, an object of this invention to provide a method of producing wood chips more effectively. Another object of this invention is to extend the service life of knives used in wood chipping. Another object is to produce wood chips at an economical rate of power consumption. A further object is to facilitate the production of uniform particles.

These and other objects I achieve by applying to the knife edge of a wood chipper, prior to the point of contacting bulk wood, a lubricant. Preferably the lubricant is a liquid; and I prefer to use wax-like or oleaginous liq- 3,328,188 Patented June 27, 1967 uids, applied in the form of particles or spray droplets of a wax emulsion or a hot melt or other thermoplastic substance. Solid lubricants iu the form of a sprayed powder may also be used.

The application of this liquid lubricant I find not only protects the knife edges from undue wear through lubricating the passage of the knife through the wood, it also permits the wood to be more cleanly cut so that regardless of the form of the wood particle, either chip, flake, or splinter, there is less tearing or grinding action resulting therefrom. One aspect for utilizing this invention may be illustrated by referring to the accompanying drawings in which:

FIGURE 1 is an elevation of a portions broken away;

FIGURE 2 is a perspective view of a typical chipper knife in detail; and

FIGURE 3 is an elevation detail a wood log.

The chipping apparatus used to illustrate this invention includes, as shown in FIGURE 1, a stationary housing 10 supporting a rotatable cylindrical drum 11. Aflixed to the external surface of the drum and arranged in any desired pattern are a plurality of knives 12. The unattached ends of the knives are beveled, as shown in FIGURE 2, the sharp edge 13 faced in the direction of rotation of the drum. The knife edges have short lengths, each length being equivalent to the size of the chip to be produced. The knives usually have slots 13' through which they may be easily clamped to the drum and as easily removed when replacement is necessary.

Attached to the sides of the drum housing 10 are plurality of nozzle heads 14, 14' and 14", each figure depicted being one nozzle or a bank of nozzles at the position indicated. These nozzles extend into the interior of the housing and they are connected by pipes 15, leading from a liquid reservoir (not shown). A liquid, such as a wax emulsion or molten wax, or a solid, such as a powdered wax, may be pumped or air-blown through the pipes to these nozzle heads, thereby causing the lubricant to be sprayed into the housing. If the liquid lubricant is in the form of a hot melt, these pipes 15 may be equipped with some auxiliary heating means, or insulation to maintain the lubricant in a liquid state.

As the drum supporting the knives rotates, wood logs 16 enter the housing either by a chain or belt conveyor 17, or alternatively by gravity through a hopper. The logs are brought into contact with the drum and held in position thus enabling the knives to cut into them. The knives are attached to the drum in such a manner that the protruding cutting edges can produce the desired shape and size of wood particle.

As the drum rotates, the lubricant, either in the liquid form, such as the wax-like or oleaginous liquid preferred according to this invention, or the powder, is sprayed into the housing. Because of the high speeds of these wood rotating chipper with of a knife cutting into chippers there is a tendency for liquids to become finely atomized within the housing. The droplets or particles are thrown about throughout the air space of the housing and become deposited on the knives and logs. Thus as the knife strikes a wood log, a coating of lubricant 18 forms about the knife and lubricates the passage of the knife surfaces through the wood fiber, as indicated in FIG- URE 3. The chips 18 having been formed are passed out of the housing. Usually the chips are thereafter passed through a screen or other size-controlling mechanism.

The exact position of the nozzle heads which direct the liquid into the container may be varied. Dilferent chipping machines may require different points of application depending upon the design, i.e. placement of knives, shape of the knife-carrying member and evacuation of chips, as well as the turbulence of the chips, the type of chip, the

type of wood being cut, and even the air currents throughout the container. For example one bank of nozzles 14' may be positioned near the knives approaching the wood log, as in FIGURE 1, so that some of the lubricant is sprayed into the upper space of the housing. Other nozzle heads may be positioned at suitable intervals around the housing. Preferably, a bank of nozzles may be directed toward the knives immediately after having passed through the wood logs and after the chip has fallen away, such as the lower nozzles 14". The knife, therefore, travels almost 360 before striking the log again during which time a more uniform coating of lubricant may be applied.

The quantity of lubricant to be sprayed will depend on the speed of the drum and on the amount of wood to be cut. A very rapidly rotating drum may require more lubricant than a slower drum. In some plants, 100 pounds of wood (about 3 cubic feet) per minute may be consumed in the chipping operation. As a result, using my preferred wax emulsion lubricant, it may be desirable to introduce as much as about a pound of wax emulsion per minute through all of the nozzles.

Usually in the preparation of wood particle boards, before the resin binder is added, the particles are initially coated with a material which water-proofs and prevents the binder from being absorbed into the center of the chip. If the binder does migrate into the chip and very little remains on the surface, the finished board may be extremely weak. Hence, the lubricating treatment of this invention often affords a dual advantage. The lubricant applied to the knife edge of the chip may become transferred to the wood chip after being cut. In addition, the droplets or powder within the housing may also become deposited upon the log and the chip. This is indicated in FIGURE 3, in which a thin film of lubricant 18 is formed between the log and the beveled surface of the knife. When the chip is later coated with resin there will be little or no penetration of the resin into the chip. The preferred amount of coating used in rendering the chip impervious to resin penetration may range from about 0.10% to about 3.0% by weight of the wood chip. Thus, if desired this coating may be applied most conveniently at the chipping stage, saving more time in the overall preparation of the particle board.

As discussed heretofore the preferred lubricants are wax-like substances which permit the knives and, if desired, the wood chips as well, to be readily coated. Those waxes which may be used in the method of this invention include paraffiuic waxes and synthetic and natural waxes. In this classification may be used scale or refined wax, slack wax, or a micro-crystalline wax. Also suitable as additives in the wax compositions for lubricating the chipper knives are natural and synthetic gums and resins, such as rosin, petroleum greases, petrolatum, refined mineral oils of preferably high viscosity, chlorinated waxes, and other high density hydrocarbon products which may be classified under the category of hot melts. In conjunction with the above waxes, the wax compositions may also include, starches, such as tapioca starch, corn starch, chlorinated starches and the like. In some instances the wax may be totally or partially replaced by synthetic resins, such as urea formaldehyde, phenol formaldehyde, polyvinyl acetate, polyvinyl chloride, and vinyl co-polymers, as well as polyethylene, polybutene, polyisobutylene and other hydrocarbons which have lubricating properties in the liquid solution emulsion or molten stage.

Also included within the scope of the lubricants of this invention are the resin binders which not only aid in the chipping operation but may also be used subsequently to bind the wood chips. By incorporating the resin binder with the lubricants hereinabove mentioned, the step of applying the binder in a separate subsequent operation may be obviated.

When solid powdered lubricants are employed, the particles of powder are preferably very small to obtain uniform coating of the knives and wood. If the lubricant is in the form of a wax emulsion, the formulation may also include emulsifiers or emulsion stabilizers to maintain the emulsion of the wax phase in water. Many types of emulsifiers may be used, such as nonionic soaps, including alkylene oxide or alkanolamine fatty acid condensate products, and cationic soaps, such as sodium salts of fatty acids.

The emulsifiable wax formulations are added to water to produce a typical liquid emulsion containing from about 30% to about 90% of water by weight of emulsion, and preferably from about 45% to about by weight of water. This preferred range insures proper fluidity of the emulsion and yet limits the amount of water to be introduced into the wood. In the formation of particle boards, excess water present in the formulation may interfere with the bin-ding of the chips. The usual acceptable maximum limit of water in the chips is about 10% by weight. If the water content of the binder-chip formulation is above this limit, the chips may have to be dried before molding.

For example a typical emulsion formulation may have the following components:

Compound: Weight percent Wax, resin, or other lubricant 15 to 60 Emulsifier 0.5 to 10 An antirust agent 0 to 1.5

Another formulation, in the form of hot melt, may consist of:

Compound: Weight percent Polyvinyl compound or polyolefin or other natural or synthetic resin 15 to 35 Wax O to 80 Natural gum 1 to 10 The compounds in this formualtion may vary, as may the weight percent, to produce emulsifiable or melting waxlike compositions having various characteristics. For example, the presence of halogen wax compounds may produce flame retarding properties; other additives may contribute excellent weathering and water repellent properties. In all respects, I find that the major improvement lies in the chipping operation, especially in extending the service life of the knives, producing better chips, and reducing power consumption, regardless of the waxes or resins used.

Other non-limiting variations may be found useful in the method and apparatus of this invention, and the foregoing description is merely to illustrate the basic concept of this invention and is in no way considered a limitation thereof.

Iclairn: I

1. In a method of forming wooden chips by feeding bull: wood against a moving system of knife edges, the improvement comprising (1) applying a lubricant to the chipper knives prior to cutting the wood and during the cutting of the wood,

(2) feeding the bulk wood against the moving system of knife edges to form the wooden chips,

(3) transferring the lubricant from the surface of the knives to the wooden chips, and

(4) coating the wooden chips with the transferred lubricant.

2. The method of claim 1, wherein the lubricant is applied in the form of a spray.

3. The method of claim -1, wherein the lubricant contains a wax-like substance selected from the group consisting of natural waxes, petroleum waxes, high-viscosity oils, natural resins and synthetic resins.

4. The method of claim 3, wherein the wax-like substance is in the form of a water emulsion.

5. The method of claim 4, wherein the water emulsion contains about 30% to about of water by weight of emulsion.

3,828,188 5 6 6. The method of claim 4, wherein the water emulsion transferred wax ranging from about 0.10% to about 3.0% contains about 45% to about 80% of water by weight of of went by Weight of the wood chip.

emulsion References Cited 7. The method of claim 3, wherein the wax is in the f f a hot me1t 5 UNITED STATES PATENTS 8. The method of claim 3, wherein the wax-like sub- 1,795,603 3/1931 Hussey. stance is in the form of a powder. 3, 04,878 9/ 1965 Peacock 24215 9. The mthod of claim 3, wherein the wax-like substance applied to the surface of the knives is transferred LAVERNE GEIGER Pnmary Examme" to the wood chip upon contact with said knife, the said 10 H. S. BELL, Assistant Examiner. 

1. IN A METHOD OF FORMING WOODEN CHIPS BY FEEDING BULK WOOD AGAINST A MOVING SYSTEM OF KNIFE EDGES, THE IMPROVEMENT COMPRISING (1) APPLYING A LUBRICANT TO THE CHIPPER KNIVES PRIOR TO CUTTING THE WOOD AND DURING THE CUTTING OF THE WOOD, (2) FEEDING THE BULK WOOD AGAINST THE MOVING SYSTEM OF KNIFE EDGES TO FORM THE WOODEN CHIPS, (3) TRANSFERRING THE LUBRICANT FROM THE SURFACE OF THE KNIVES TO THE WOODEN CHIPS, AND 